Flame tubes for use in combustion systems of gas turbine engines



EMS OF GAS TURBINE ENGINES Aug. 1, 1961 F. BONSALL ETAL FLAME TUBES FOR USE IN COMBUSTION SYST 5 Sheets$heet l /V V5 70195 LL, 06654550,

L HOMl/Y/ST 07121 Original Filed Feb. 28, 1955 Arvo EBB/U620 /o/ve y ASsEy B Y rim 1.7 9/

Aug. 1, 1961 FLAM F. BONSALL ET AL 2,994,196

E TUBES FOR USE IN COMBUSTION SYSTEMS OF GAS TURBINE ENGINES Original Filed Feb. 28, 1955 5 Sheets-Sheet 2 Alva eezumep Aug. 1, 1961 FLAME F. BONSALL ET AL 2,994,196

TUBES FOR USE IN COMBUSTION SYSTEMS OF GAS TURBINE ENGINES Original Filed Feb. 28, 1955 5 Sheets-Sheet 3 BY M F. BONSALL ET AL FLAME TUBES FOR USE IN COMBUSTION SYSTEMS OF GAS TURBINE ENGINES Aug, 1, 1961 5 Sheets-Sheet 4 Original Filed Feb. 28, 1955 NSALL, uo 5684/4/20 s/away MASSEY ATT Y5 Aug. 1, 1961 F. BONSALL ET AL 2,994,196

FLAME TUBES FOR USE IN COMBUSTION SYSTEMS OF GAS TURBINE ENGINES Original Filed Feb. 28, 1955 5 Sheets-Sheet 5 nvvevmzs eA/vk Ed VSALL, 05054550,

atct 2,994,196 Patented Aug. 1, 1961 2,994,196 FLAME TUBES FOR USE IN CONEUSTION SYS- TEMS F GAS TURBINE ENGINES Frank Bonsall, deceased, late of Bristol, England, by

Audrey Vivien Bonsall, administratrix, Westbury-on- Trym, and Bernard Sidney Massey, Bristol, England; said Frank Bonsall and Massey, assignors, by mesne assignments, to Bristol Acre-Engines Limited, Bristol, England Original application Feb. 28, 1955, Ser. No. 491,098. Divided and this application Aug. 25, 1959, Ser. No. 837,319

Claims priority, application Great Britain Mar. 2, 1954 3 Claims. (Cl. 60-3965) This application is a divisional application of United States application Serial No. 491,098 filed on February 28, 1955 by Frank Bonsall and Bernard Sidney Massey entitled, Flame Tubes for Use in Combustion Systems of Gas Turbine Engines.

This invention relates to flame tubes for use in the combustion systems of gas turbine engines.

The object of the present invention is to provide an improved flame tube the improvement being directed to cooling arrangements for cooling those parts of the flame tube surrounding the primary combustion zone.

One embodiment of the present invention will now be described merely by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a longitudinal section taken through the axis of a flame tube according to the invention,

FIGURE 2 is a view in the direction of arrow 5 in FIGURE 1 showing in partial end view 3 of the flame tubes of FIGURE 1 joined together,

FIGURE 3 is a view in the direction of arrow 6 in FIGURE 2,

FIGURE 4 is a view on line 77 in FIGURE 3,

FIGURE 5 is a transverse section on line 88 in FIGURE 4 showing parts of two of the flame tubes of FIGURE 1 joined together,

FIGURE 6 is a view in the direction of arrow 9 in FIGURE 5, and

FIGURE 7 is a diagram showing in partial end View the shape of a transitional part of the flame tube of FIGURE 1 taken on line 10-10 in FIGURE 1.

Referring to the drawings, the combustion equipment comprises a set of seven flame tubes which are secured together and are arranged round the central axis of the gas turbine engine. Each flame tube comprises an annular inlet portion indicated at 15, which is connected through a smoothly-curved transition portion 17 to a cylindrical shell 14 forming the main portion of a tubular body part indicated generally by reference numeral 10. The cylindrical shell 14 communicates through another transition portion 12 with an outlet passage part of which is generally indicated at 11. The body part 10 of the tube encloses the combustion space 13.

Referring to FIGURE 1 of the drawings, the inlet end portion comprises a tubular member 16 defining an inlet opening for primary combustion air, and surrounding frusto-conical walls 76, 78 forming the inlet end of the flame tube. Swirl vanes 18 project inwardly from the member 16 to a ring .19 closely surrounding the outlet end of an atomizing burner (not shown). A further set of vanes 20 extend to a ring 21, the inner surface of which is of part spherical shape and houses spherically surfaced bearing elements 22 by means of which the flame tube may be slidingly mounted upon a cylindrical surface of the burner so that the burner supports the forward end of the flame tube in a manner allowing for angular or endwise movements. Secondary air for the combustion of fuel sprayed into the chamber through the burner is admitted through holes 24 provided in the cylindrical shell 14 of the body part 10.

The outer frusto-conical wall 76 is in this construction formed integrally with the transition portion 17 and the cylindrical shell 14, and its radially inner edge is disposed slightly downstream of and radially spaced from the upstream edge of the tubular member 16, so as to provide an annular opening admitting cooling air to the space 77 formed between the walls 76, 78. The inner frusto-conical wall 78 has its radially-inner edge secured to the downstream end of the tubular member 16, and its radially-outer sedge adjacent but spaced from the outer frusto-conical wall 76 adjacent the junction of the latter with the transition portion 17. Swirl vanes 79 are disposed in the gap thus provided and serve to impart a swirl round the longitudinal axis of the flame tube to cooling air flowing from the space 77 through the gap and over the inner surface of the walls of the transition portion 17 and the cylindrical shell 14.

The transitional part 12 is circular in shape at its forward end as particularly shown in FIGURE 7 and is connected to the rear end of the shell 14 by a butt weld 80, a reinforcing ring 81 overlapping the butt joint on the inside and also being welded in position. At its rear endthe transitional part is shaped as a segment of an annulus where it has inner and outer spaced concentric walls 82, 83 (see FIGURE 7) and between its ends has transitional cross-sectional shapes as indicated by the lines 84 in this figure.

The inner concentric wall 82 has a rearward extension which forms the inner concentric wall 28 of the outlet passage part 11 as before while the outer concentric wall of the part 11 is formed by a separate rigid precision cast segment 86 butt welded as at 87, to the rear edge of the wall 83 of the part 12. The radially extending side walls of the part 11 are formed by members 87 and 88 (see FIGURES 4 and 5) welded as at 89, 90 to the radially extending walls at the rearward end of the part 12, and to depending flanges 91 on the segment 86. The members 87, 88 are provided with flat sealing faces 92, 93 which are arranged to engage corresponding flat faces. on the adjacent flame tubes as shown in FIGURE 5, so that a seal is, provided between them. These flat faces also extend uninterruptedly over surfaces of lugs 95, 9.6 which are formed integrally with the segment 86 so as to be upstanding from the outside thereof, the lugs being provided with bores. to receive a nut and bolt 43 to hold the adjacent flame tubes together.

As shown in FIGURE 2, the faces 92, 93 at opposite sides of each flame tube lie in planes which include an angle which is one seventh of 360 so that seven flame tubes arranged with their faces 92, 93 in juxtaposition form a complete outlet passage which is a circular an In FIGURE 2 is also shown the cylindrical shells.

nulus. 14 of the flame tubes as seen in the axial direction, and it will be seen that they remain spaced from one another on opposite sides of the planes containing the faces 92, 93.

The segment 86 and the inner concentric wall 28 of the part 11 are perforated to receive the outer and inner ends of a row of hollow sheet metal turbine-nozzle guide blades arranged in equally spaced relation so as to form a complete circle of blades when seven of the flame tubes are bolted up together, the perforations corresponding in shape to the shape of the blades in crosssection. The inner ends of the blades of each flame tube are attached to the wall 28 of the outlet passage part of the flame tube by means of sheet metal members 46 which are spot welded to the wall as indicated at 47 and have upturned flangeslying along side the parts of the blades which project through the wall, the edges of" these flanges and the edges of the blades being welded together. This method of attaching hollow blades to a supporting member is more fully described in the specification accompanying United States patent application Serial No. 407,053. At their outer ends the blades 45 each have their edge flush with a raised lip 100 (see FIGURE 4) formed integrally with the segment 86 around the perforations which receives the outer end of the blade, and the edge of the blade is welded to the lip as at 101.

The segment 86 has a thickened rim 102 along the whole of its rear edge which provides an abutment face 103 which takes the thrust of the flame tube, the rims 102 on a set of seven flame tubes when assembled together providing an annular abutment surface which also acts as a sealing face.

A set of seven of the flame tubes now being described are intended to be contained within an annular air casing having an outer substantially cylindrical wall 61 (see FIGURE 1), and an inner concentric substantially cylindrical wall 62. The rear end of the wall 61 is attached to an outer turbine casing: which has a ring-like extension 105 extending forwardly within the outer wall 61 of the air casing. The ring-like extension has a thickened rim which is adapted to support the forward end of a turbine stator casing 106 housing a turbine rotor (not shown), and has a forwardly facing annular abutment face 107 against which the abutment faces 103 on the flame tubes abut. The rim is also provided with recesses to receive locating dogs 110 (see FIGURES 2, 3 and 4) projecting rearwardly from the segments 86 of a set of flame tubes. The flame tubes of a set are thus allowed freedom to expand and contract relatively to the outer air casing while being effectively held concentric with respect to the axis of the air casing and being prevented from transverse movement.

The resultant thrust of the gases in and around the set of flame tubes upon the flame tubes is in the rearward direction, and since the flame tubes are freely mounted for axial movement at their forward ends (on the atomizing burners) this thrust is taken on the abutment face 107. The engagement between the face 107 and the faces 103 also provides a peripheral seal around the outside of the set of flame tubes between the air casing and the turbine. This seal ensures that the majority of the relatively cooler air around the outside of the flame tubes and between the flame tubes and the outer wall 61 of the air casing passes into the open ends of the blades 45 and through the blades to cool them. A number of small passages 112 (see FIGURE 2) are provided, however, through which air is allowed to pass into the turbine stator casing 106, appropriate passages being provided in the abutment face 107.

The inner wall 62 of the air casing is provided at its rear end with a conically shaped part 114 following the general contour of the flame tubes as seen in longitudinal section. At its rearward edge the part 114 carries a grooved member 122 containing a piston ring" 123 which is pressed by a light backing spring (not shown) into sealing engagement with generally U-section members 115 attached one to the outer side of the inner concentric wall 28 of the outlet part 11 of each of the flame tubes so as to straddle the open ends of the blades 45. The U-section members 115 are precision castings and are formed with outwardly directed flanges 116, 117 at the tops of their side walls, the rearward flange being entered and located in a fold 119 in the rear edge of the extension forming the wall 28 and the forwardly extending flange being secured against the wall 28 by means of a joggled strip 120 welded to the wall 28.

The members 115 of a set of seven flame tubes assembled together abut one another to define with the walls 28 of the outlet parts of the flame tubes an annular chamber which receives the cooling air passing through the hollow blades 45 and this air is discharged from the chamber through holes 121 downstream of the seal between the members and the part 114 of the inner wall 62 of the air casing and entering the working fluid duct through the turbine.

In the construction described, it will be noted that the butt joints between the outlet passage parts of the flame tubes assembled in a set are made oblique to the direction of gas flow so that they may be accommodated between an adjacent pair of blades 45 one on one flame tube, and the other on another flame tube.

During the assembly of an engine, a set of seven flame tubes as described with reference to the drawings may be connected together by the bolts 43 and then inserted endwise as an assembly into the annular air passage formed between the walls of the air casing, the assembly being withdrawn in the same way as and when necessary. Alternatively a completely annular flame tube and ring of turbine-nozzle guide blades could be made as a single unit for insertion into and withdrawal from the annular air passage or again, the individual flame tubes of a set may first be inserted into the annular air passage, the flame tubes being bolted together by the bolts 43 after being located in their required positions.

We claim:

1. A flame tube for use in combustion equipment on a gas turbine engine and comprising a tubular member defining an inlet for primary combustion air, a divergent inlet portion coaxially surrounding the tubular member and comprising frusto-conical inner and outer walls spaced from each other throughout their length, the inner wall having a radially-inner edge which is secured to the tubular member and the outer wall having a radially-inner edge which is radially spaced from the tubular member, a tubular body portion disposed downstream of the inlet portion and enclosing the combustion space, and a smoothly-curved annular transition portion which interconnects the outer frusto-conical wall and the tubular body portion to form them into a smooth continuation of one another, said frusto-conical inner wall having its outer edge disposed adjacent the junction of the outer wall and the transition portion leaving a peripheral gap through which air entering the space between said walls through the space between the tubular member and the inner edge of the outer frusto-conical member can flow over and in contact with the transition portion.

2. A flame tube for use in combustion equipment on a gas turbine engine and comprising a tubular member defining an inlet for primary combustion air, a divergent inlet portion coaxially surrounding the tubular member and comprising fr-usto-conical inner and outer Walls spaced from each other throughout their length, which inner wall has a radially-inner edge which is secured to the tubular member, the outer wall having a radiallyinner edge which is radially spaced from the tubular member, and the tubular member extending in an upstream direction beyond said inner edge of the outer wall, a tubular body portion disposed downstream of the inlet portion and enclosing the combustion space, and a smoothly-curved annular transition portion which interconnects the outer frusto-conical wall and the tubular body portion to form them into a smooth continuation of one another, said frusto-conical inner wall having its outer edge disposed adjacent the junction of the outer wall and the transition portion leaving a peripheral gap through which air entering the space between said walls through the space between the tubular member and the inner edge of the outer frusto-conical member can flow over and in contact with the transition portion.

3. A flarne tube for use in combustion equipment on a gas turbine engine and comprising a tubular member defining an inlet for primary combustion air, a divergent inlet portion coaxially surrounding the tubular member and comprising frusto-conical inner and outer walls spaced from each other throughout their length, the inner W ll having a radially-inner edge which is secured to the tubular member and the outer wall having a radially-inner edge which is radially spaced from the tubular member, a tubular body portion disposed downstream of the inlet portion and enclosing the combustion space, a smoothly-curved annular transition portion which interconnects the outer frusto-conical wall and the tubular body portion to form them into a smooth continuation of one another, said frusto-conical inner wall having its outer edge disposed adjacent the junction of the outer wall and the transition portion leaving a peripheral gap through which air entering the space between said walls through the space between the tubular member and the inner edge of the outer frusto-conical member can flow References Cited in the file of this patent UNITED STATES PATENTS Winter June 15, 1954 FOREIGN PATENTS 697,027 Great Britain Sept. 16, 1953 

